Default pure virtual destructor

Question

In C++11, we are able to declare a destructor to be auto generated:

struct X {
  virtual ~X() = default;
};

Also, we can declare a destruct

Answer 1

In order to define a pure virtual method, you need a separate definition from the declaration.

Therefore:

struct X {
    virtual ~X() = 0;
};

X::~X() = default;